iOS apps can be installed on Apple TV, they just can't be launched (yet?)
Developer Steve Troughton-Smith has discovered that you can install iOS apps on the new iOS Apple TV, you just can't launch them yet because Apple TV lacks the capacity to do so.
So, not only is the AppleTV set up for installing applications (of UIDeviceFamily 3), but the installation actually works
Of course, adding that capability will no doubt be high on the jailbreak to-do list... if Apple themselves don't do it first. (Fingers crossed).